module GraphRewriting.Layout.Gravitation where
import Data.View
import Data.Vector.Class
import Data.Vector.V2
import Data.Functor
import GraphRewriting.Graph.Types
import GraphRewriting.Graph.Read
import GraphRewriting.Layout.Position
import GraphRewriting.Layout.Force
centralGravitation ∷ View Position n ⇒ Node → WithGraph n Force
centralGravitation = fmap (attraction (vpromote 0) . examine position) . readNode
gravitation ∷ View Position n ⇒ Node -> Rewrite n Force
gravitation node = do
n ← examine position <$> readNode node
ns ← fmap (map $ examine position) (mapM readNode =<< readNodeList)
return $ fsum [attraction n' n | n' ← ns]